1. Field of the Invention
The present invention relates to a scientific calculator capable of function conversion operations, and more particularly to a scientific calculator capable of coordinate transformation.
2. Description of the Prior Art
Conventional scientific calculators capable of coordinate transformation (for example, a type provided with a one-line numerical value display unit capable of displaying only one numerical value or one calculation result value) can not display simultaneously coordinates composed of two numerical values. Therefore, it has been predetermined which of the coordinate calculation result values is to be first displayed after completing coordinate calculation. Thereafter, confirming the numerical value, the user operates a numerical value replacement key ([x.rarw..fwdarw.y] key) for replacing the numerical value currently displayed by the numerical value display unit with the other numerical value stored in a data storage unit (RAM) of the calculator, thereby confirming alternately the two numerical values produced from the calculation.
An example of a transformation operation is from rectangular coordinates (x, y) to polar coordinates (r, .theta.). This transformation requires the confirmation of the input order of the values "r" and ".theta." for executing a reverse transformation to go back co the rectangular coordinates following the display of the calculation result on the polar coordinates. In other words, when the value "r" is displayed immediately after a polar coordinate transformation operation, it has been conventionally required to display the value ".theta." at the display unit before executing the rectangular coordinates transformation.
FIG. 7 is an exterior view of a conventional scientific calculator. Referring to FIG. 7, the reference numeral 71 denotes a display unit of the calculator. The display unit 71 includes a numerical value display unit 71a and a [2ndf] symbol display unit 71b for indicating a second function selection condition.
The reference numeral 72 denotes a key input unit. The reference numeral 72a denotes a coordinate transformation key for executing a first function of polar coordinate transformation calculation in a [.fwdarw.r.theta.] key condition as well as a second function of rectangular coordinate transformation calculation in a [.fwdarw.xy] key condition.
The reference numeral 72b denotes a [x.rarw..fwdarw.y] key (numerical value replacing key) for replacing the value displayed at the moment with the value stored inside the calculator, while the reference numeral 72c denotes an argument key for entering a numerical value. The reference numeral 72d represents four arithmetic calculation keys [+], [-], [.times.], and [.div.], while the reference numeral 72e denotes an equal key [=] for executing calculation such as the four arithmetic calculations. The reference numeral 72f denotes an [ON/C] key for clearing the calculation result value or turning on the calculator powered off, while the reference numeral 72g is a [2ndf] key (2nd function key) for designating the second function.
FIG. 8 is a chart showing a coordinate transformation calculation example according to a conventional technique.
The example shown in FIG. 8 is a calculation example for transforming rectangular coordinates (x=1, y=2) into polar coordinates (r, .theta.) and shows the contents of processing with regard to each item.
Item 1: Data inside the calculator is cleared by operating the [ON/C] key.
Item 2: An X coordinate value "1" is entered.
Item 3: The numerical value currently displayed (X coordinate value) is replaced by the numerical value internally stored.
Item 4: A Y coordinate value "2" is entered.
Item 5: The rectangular coordinates (1, 2) are transformed into the polar coordinates (r, .theta.). Between the calculation result values, the value r (2.236067977) is displayed.
Item 6: The numerical value currently displayed (value r) is replaced by the numerical value stored inside (value .theta.), and then the value .theta. (63.43494882) is displayed.
Item 7: The value r (2.236067977) is displayed again.
Item 8: A reverse transformation is executed. However, since the value "r" is currently displayed, no complete reverse transformation for the transformation executed as above is executed. The reason of the above is that the value currently displayed is used as the value ".theta." in executing the calculation of [.fwdarw.xy], where the values "r" and ".theta." are exchanged. Consequently, a rectangular coordinate transformation is executed for the coordinates (63.43494882, 2.236067977).
For the above-mentioned reasons, display of only one numerical value has been permitted for two calculation result values in a scientific calculator based on the conventional technique, and therefore it has been unable to discriminate which of the numerical values is currently displayed. Furthermore, when executing a reverse transformation calculation for the transformation result executed just now, the transformation operation has been required to be executed always after displaying the value ".theta." (polar coordinate value) or the value "y" (rectangular coordinate value).
Therefore, the user is required to remember which of the calculation result values is currently displayed, which easily results in an error of designating an incorrect coordinate value in the reverse transformation calculation process immediately after the transformation calculation as described on Item 8 in FIG. 8.
As a means for resolving the above-mentioned drawbacks, there is proposed for a pocket computer a display method including a multi-line display unit comprised of a specified number of figures and a plurality of lines allowing many calculation equations to be displayed, thereby assuring easy confirmation of all the calculation equations and preventing the possible confusion between the calculation equations and calculation result values (JP 60-186928).
However, the above-mentioned display method is for a pocket computer having a multi-line display unit comprised of at least two lines. In other words, there is provided no disclosure of a display method for easily confirming which of two calculation result values is currently displayed when two calculation result values exist in a scientific calculator having a numerical value display unit capable of displaying a numerical value only in one line.